The present invention relates in general to telephone switching circuits and, in particular, to methods and devices for constructing very large integrated voice and data switching systems which are highly modular.
Key features not found in prior art approaches include:
a modular circuit switch PA0 a modular packet switch PA0 the use of the circuit switch to interconnect to packet switching modules PA0 the making of each element of the system a data "subscriber" of the system along with the external users so that external user data and internal control data can be switched by the same mechanisms. PA0 a modular circuit switch handling 64K bps digital circuits in many 24 channel multiplex groups. These may carry digitized voice, circuit switched data, or data packets. PA0 Subscriber and trunk termination devices which generate one or more 24 channel groups. Normally one (or more) of the 24 channels in each group will be used to carry both system control data and user data a combined packetized stream with the packets of the subscribers and the system control data comingled. The data circuit or circuits from each group are semi-permanently connected ("nailed through") the circuit switch to 24 channel multiplexed circuits which now consist entirely of 64K bps data circuits from various sources. These combined data circuits are in turn connected to: PA0 a modular packet switch in which each module has at its input one of these combined circuits consisting of 24 64K bps packet streams.
In a typical application, the overall system consists of:
The architecture of the system simplifies the mechanization of the control system as controlled devices within the system are also "subscribers" of the packet switching system in addition to the external or regular subscribers. This much of the system control traffic can use the same mechanisms as the user data.
The modules of the packet switch are then interconnected, for example, in a fashion which logically resembles a three-stage space switch with interconnections at the 64K bps level. These connections are actually provided with further semi-permanent connections in the circuit switch.
Finally, a redundant control system is provided to control the whole system.